1. Field of the Invention
The present invention relates to a toner composition and a method of preparing toner using the same, and more particularly, to a toner composition having improved particle diameter and charge quantity characteristics of toner as well as improved dispersion property of a coloring agent, and a method of preparing toner using the toner composition.
2. Description of the Related Art
Recently, demand for printers has gradually increased with development in computer industries. Accordingly, the amount of toner used has also increased.
Toner particles used for displaying an image are generally prepared by a grinding method. According to the grinding method, a polymer bonding resin, a coloring agent and a charge controller, etc. are blended in a dry condition. Then, the mixture is melt-mixed and cooled. The resultant is ground to fine toner particles.
Toner particles prepared by the above method have a wide distribution of particle diameters. Because toner particles outside a predetermined diameter range must be excluded, it is an economically unfavorable method. Limitation in dispersion of the charge controller and the coloring agent, and the shape of the toner particles often leads to an unsatisfactory resolution. To solve these problems, spherical toner particles have been prepared by polymerization technique.
This polymerization technique is classified into an emulsion polymerization method and a suspension polymerization method. According to the emulsion polymerization method, the final toner particle is usually smaller than 5.mu.m in diameter. It, however, causes an adverse effect on human body. As a result, it would be is difficult to use these particles to preferred printers. This is why the suspension polymerization method is a preferred polymerization method.
A method of preparing toner by the suspension polymerization method is described as follows.
Water is used as a reaction medium, and a monomer for a binding resin, a charge controller, a stabilizer, a lubricant and a coloring agent are added to the reaction medium, and then polymerization is performed.
After the polymerization is completed, spherical particles sediment inside the reaction mixture. The obtained particles are filtered and then dried, producing in toner particles.
Phosphate or hydrophobic silica is used as the stabilizer. When using phosphate as the stabilizer, however, the particle diameter of the final toner particles tends to be very large, i.e., over approximately 35 .mu.m, and the particle diameter distribution shows a wide variation ranging from a few to hundred micrometers in diameter. These particles contributes to lowering charge characteristics, and thus do not have proper properties as toner.
On the other hand, when the hydrophobic silica is used as the stabilizer, it is very difficult for the silica to be dispersed into the water. As a result, the polymerization reaction cannot occur. Therefore, the hydrophobic silica must be solubilized in an organic solvent, such as methanol, before it could be miscible with the other constituents of the toner composition for the polymerization.